1. Field of the Invention
The present invention relates to a valve apparatus, more particularly, to a valve apparatus suitable for being used as a shunt valve embedded in the body for adjusting the pressure of the cerebrospinal fluid or the like and a valve system comprising the valve apparatus and a control device for controlling set pressure of the valve apparatus.
2. Description of the Prior Art
Japanese Patent Laid-Open No. 40063/1985 discloses a constitution in which there is provided in a flow path of the cerebrospinal fluid or the like for adjusting the pressure of the cerebrospinal fluid or the like, a shunt valve provided with a leaf-like spring one end portion of which is brought into contact with a ball serving as a valve element, other end portion of which is engaged with a cam face in a shape of a spiral staircase integrally formed with a rotor of a multiple poles step motor element and which changes press force of a ball by the spring by changing a flexing amount of the spring by moving the engaged end portion of the spring in an axial direction of the rotor in accordance with rotation of the cam face in correspondence with rotation of the rotor for treatment of hydrocephalus or the like.
However, in the case of the shunt valve apparatus, the thickness of the shunt valve apparatus is difficult to increase so considerably since the flexing direction of the spring is aligned to the thickness direction of the valve apparatus and therefore, when a comparatively wide range of pressure adjustment is made feasible by one kind of the shunt valve apparatus, it is necessary to comparatively increase a variation in press force exerted on the ball-like valve element even with a very small flexing amount of the spring and accordingly, even a very small dispersion in the flexing state of the spring is liable to amount to a large dispersion in the press force and it is not necessarily easy to adjust the press force to a predetermined value. Further, in order to change the flexing amount of the spring to adjust set pressure of the shunt valve apparatus, it is necessary to arrange a pressure adjusting or controlling device (shunt valve adjusting element) having a plurality of pieces of electromagnets along a circumferential direction such that the center of the device coincides accurately with the center of the multiple poles step motor element embedded in the body and therefore, the pressure adjustment is difficult to carry out easily.
Further, there is also known in, for example, Japanese Patent Laid-Open No. 170749/1996, a valve apparatus in which one end portion of a leaf spring bent substantially in a semicircular shape is fixed to a rotor having a permanent magnet, a peripheral face of a middle portion of the leaf spring extended to bend in the semicircular shape from the fixed end portion to a free end, is made to be able to be brought into contact with a valve element in a ball-like shape and press force of the ball by the spring is changed in accordance with a change in a position of bringing the spring and the ball into contact with each other in accordance with rotation of the rotor.
However, according to the valve apparatus, in order to be able to accurately adjust the press force exerted to the ball, a leaf spring in a specific bent state in substantially a semicircular shape is indispensable and it is not necessarily easy to realize a two-dimensional shape of such a spring with the least dispersion.
The invention has been carried out in view of the above-described points and it is an object thereof to provide a valve apparatus which is easy to set the press force exerted on a valve element with high accuracy and a valve system including the valve apparatus.
In order to achieve the object, according to an aspect of the invention, there is provided a valve apparatus comprising a long-sized elastic member a base end portion of which is fixed and a front end portion of which is brought into contact with a valve element, and a movable member movable actually linearly along a longitudinal direction of the elastic member between both end portions of the elastic member and having a fulcrum portion for flexing the elastic member between the both end portions of the elastic member.
According to the valve apparatus of the invention, there is provided the movable member movable actually linearly along the longitudinal direction of the elastic member between the fixed base end portion of the long-sized elastic member and the front end portion brought into contact with the valve element and having the fulcrum portion for flexing the elastic member between the both end portions of the elastic member and accordingly, the press force exerted on the valve element by the elastic member can be adjusted by adjusting the position of the fulcrum portion by adjusting the position of the movable member in the longitudinal direction of the elastic member to thereby change the spring constant of the elastic member between a position of supporting and pressing the elastic member by the fulcrum portion and a position of supporting (contacting) the elastic member by the valve element. Further, the elastic member is long-sized and the position of the movable member is moved in the longitudinal direction of the elastic member in order to change the flexing state of the elastic member and accordingly, an amount of moving the movable member can be increased even for slightly changing the flexing state of the elastic member. Therefore, the flexing state is easy to adjust accurately. Further, the elastic member is fixed at the base end portion and is brought into contact with the valve element at the front end portion and supported by the valve element to thereby bring about a doubly supported state and accordingly, not only the elastic member can be held stably but also a flexing deformation is added at the middle portion in the longitudinal direction of the elastic member in the doubly supported state by the fulcrum portion and therefore, there is less concern of concentrating stress at one portion of the elastic member, the flexing state of the elastic member is easy to control accurately and there is less concern of variation or deterioration in the flexing characteristic of the elastic member even when the elastic member is used for a long period of time.
The elastic member is typically constituted by a leaf spring. However, when desired, the elastic member may be a structure of an elastic member material capable of setting the characteristic of the flexing deformation in a desired manner.
When the elastic member comprises a leaf spring, at least one of a thickness, a width, an inclination and a contour line of a face pressed by the fulcrum portion of the spring may be changed in accordance with a position of the spring in the longitudinal direction such that the press force of the valve element by the spring is varied in a desired pattern in accordance with moving the fulcrum portion in the longitudinal direction of the spring. In this case, the way of varying the press force may be constituted such that when the movable member is moved in a direction of approaching the valve element along the longitudinal direction of the spring, the press force of the valve element by the spring is increased actually linearly or increased sublinearly. Further, a degree of the increase (for example, inclination in the linear case) may be made comparatively large or small. With regard to the width of the spring, the width may be varied such that, for example, the more proximate to the front end portion, the larger the width, or conversely, the smaller the width, the width is varied along the longitudinal direction by other mode (for example, such that the more proximate to the front end portion, the larger the width in a range from a middle predetermined position to the front end portion or the width is large at a central portion in the longitudinal direction and is small at both end sides or the width is small at the central portion in the longitudinal direction and is large at the both end sides or the width is varied periodically at a predetermined pitch along the longitudinal direction). The same goes with the thickness and the thickness may be varied instead of or along with varying the width of the spring along the longitudinal direction or the thickness may be varied by the above-described mode while the width is varied. A total of the thickness in the width direction may be varied or the thickness may be varied such that there is provided a projected shape or a recess groove extended in a desired range along the longitudinal direction at a portion in the width direction. Further, the spring may be fabricated such that while the thickness stays substantially in a constant state, in view of a cross-sectional face orthogonal to the longitudinal direction, a recess portion is formed on one surface and a projected portion is formed on other surface. With regard to the inclination, when the spring is formed in a flat plate shape, the inclination may be constituted such that a relative height between the front end portion and the base end portion of the spring is changed and the spring is actually extended in a direction in parallel with the direction of moving the movable member on a front end side or a base end side of a position of supporting the spring by the fulcrum portion or the spring may be inclined slightly in the direction of moving the movable member in either of the directions. In the case of the spring in the flat plate shape, a change in the inclination amounts to a change in the contour of the upper face of the spring. Meanwhile, the contour of the upper face may be changed by changing the thickness of the spring.
The fulcrum portion may be a protruded portion or a projected portion formed at a position of the movable member opposed to one face of the elastic member or may be a rolling element such as a ball or a roller rollably contained and supported by a main body portion of the movable member. A front end of the protruded portion or the projected portion which is brought into contact with the surface of the elastic member for pressing the surface, may be formed in a dot-like shape or a linear shape extended in a direction intersecting with the longitudinal direction of the elastic member, typically, a direction orthogonal thereto. A length of projecting the fulcrum portion from the main body portion of the movable member to the surface or the spring is typically maintained constant. However, when desired, the projected length per se may be varied in accordance with the position of the movable portion along the longitudinal direction of the spring. Typically, the fulcrum portion is projected from a surface of the main body portion of the movable member opposed to a pressed face of the elastic member. However, when desired, an arm portion may be provided at the main body portion of the movable member and the fulcrum portion may be provided at the arm portion.
The valve element is typically constituted by a ball. However, when desired, the valve element may be formed in other shape.
The movable member is typically constituted by a slider slidable along a wall of the valve apparatus main body. However, the movable member may penetrate the wall of the valve apparatus main body or a guide shaft via a rollable ball or the like and may be movable relative to the guide shaft. The movable member may be constituted by a mover, that is, a moving piece of a linearly driven step motor element or may be coupled to a conversion mechanism for converting rotation of a rotor of a step motor element of a rotary type into linear motion. Further, the motor is an electric motor and is preferably constituted by a step motor element such that the position of the movable member is easy to control firmly from outside. However, when desired, the motor may be constituted by other kind of motor. Further, the step motor element is preferably constituted to be magnetized in a direction orthogonal to the longitudinal direction of the elastic member. In that case, by applying a pulse-like magnetic field which is spatially uniform in a direction orthogonal to a direction of extending the elastic member from outside, the position of the movable member can be changed by driving the step motor element via the stator and accordingly, positioning of a drive source relative to the step motor element can be carried out easily and firmly. Further, the step motor element is preferably constituted to produce force for holding the movable member at a stationary position when the stator is not applied with the magnetic field. In that case, there is less concern of varying the position of the movable member by mechanical impact, magnetic or electromagnetic disturbance or the like from outside or the variation of the position can be minimized.
Although the valve apparatus may be used other than the field applied to the human body such as medical use or the like, typically, the valve apparatus is constituted to be able to surgically embed into the body to be used as a shunt valve, for example, for the ventricle of the brain xe2x80x94the abdominal cavity shunt, the ventricle of the bran xe2x80x94the ventricle of the heart shunt or the like such that pressure of a related fluid in the body can be noninvasively adjusted with a purpose of treatment of hydrocephalus, cerebral tumor, subarachnoid cyst or the like and can have a size of about several cm or smaller suitable for being used in adjusting the pressure of the cerebrospinal fluid or the like.
The above-described valve apparatus is preferably used by being combined with a movable member position control device in which a stator of a step motor element is applied with a pulse-like magnetic field which is directed in a direction actually orthogonal to the longitudinal direction of the elastic member and which is actually uniform over an entire length in the direction of moving the movable member in order to move the movable member in the longitudinal direction of the spring to thereby constitute a valve system. In this case, control of the position of the movable member can be carried out firmly by applying a desired magnetic field on the stator by only arranging the movable member position control device a direction of which is aligned to the surface of the body such that a pulse-like magnetic field is applied in the direction orthogonal to the longitudinal direction of the elastic member.